Currently starring in Les Miserables, the 47-year-old mum of three, including pop star Eliza Doolittle, explains how she got through it.

In Les ­Miserables I play a ­prostitute – Whore 1. Being in the film brought back a lot of memories of my time in New York and being pregnant with Eliza. I was 21 and playing Eponine on Broadway in Les Mis.

As I’d grown up eating healthily and exercising, I thought I’d sail through my pregnancy. But it quickly became obvious that wasn’t going to happen. I was constantly nauseous and lost count of how often I was vomiting. I couldn’t even brush my teeth. Every time I tried, I’d throw up.

I remember thinking, ‘This isn’t what it says in the pregnancy books’. I was so ill I had to keep going into hospital and being drip-fed. I had to return to London, where in the end I spent five months in bed before Eliza was born.

Doctors tried giving me raspberry leaf tea, flat Diet Coke too, but nothing worked. I even tried having some acupuncture. Some people say women can be allergic to pregnancy and perhaps my hormones were just too strong for my body.

One positive was that doctors told me I shouldn’t worry too much about the baby’s health because your baby will take everything from you.

Eliza was born very quickly and ­painlessly, and she’s a healthy adult as are my two boys Nat and Felix.

And despite the misery of that first pregnancy, once you see the end result – a beautiful baby – all the nausea is worth it.

I’ve been reading about Kate’s ­pregnancy and all I would say to her is that it doesn’t necessarily get better with subsequent ­pregnancies. I was in bed for five months with Eliza, slightly longer with Nat, who is now 23, and for Felix, who is 17 now, it was the entire nine months.

I was in pain from being starving and I went down to six stone. It was a nightmare, but at least I knew there would be an end to it and my ­symptoms vanished the second Felix was born.

One lesson I did learn by my third pregnancy was that chewing gum helped me cope. That’s my tip to Kate.